-//===-- Support/SCCIterator.h - SCC iterator --------------------*- C++ -*-===//
-//
+//===-- Support/SCCIterator.h - Strongly Connected Comp. Iter. --*- C++ -*-===//
+//
// The LLVM Compiler Infrastructure
//
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
-//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
//===----------------------------------------------------------------------===//
//
-// This builds on the Support/GraphTraits.h file to find the strongly connected
+// This builds on the llvm/ADT/GraphTraits.h file to find the strongly connected
// components (SCCs) of a graph in O(N+E) time using Tarjan's DFS algorithm.
//
// The SCC iterator has the important property that if a node in SCC S1 has an
// edge to a node in SCC S2, then it visits S1 *after* S2.
-//
+//
// To visit S1 *before* S2, use the scc_iterator on the Inverse graph.
// (NOTE: This requires some simple wrappers and is not supported yet.)
//
//===----------------------------------------------------------------------===//
-#ifndef SUPPORT_SCCITERATOR_H
-#define SUPPORT_SCCITERATOR_H
+#ifndef LLVM_ADT_SCCITERATOR_H
+#define LLVM_ADT_SCCITERATOR_H
-#include "Support/GraphTraits.h"
-#include "Support/iterator"
+#include "llvm/ADT/GraphTraits.h"
+#include "llvm/ADT/iterator"
#include <vector>
#include <map>
+namespace llvm {
+
//===----------------------------------------------------------------------===//
///
/// scc_iterator - Enumerate the SCCs of a directed graph, in
nodeVisitNumbers[N] = visitNum;
SCCNodeStack.push_back(N);
MinVisitNumStack.push_back(visitNum);
- VisitStack.push_back(make_pair(N, GT::child_begin(N)));
- //DEBUG(std::cerr << "TarjanSCC: Node " << N <<
- // " : visitNum = " << visitNum << "\n");
+ VisitStack.push_back(std::make_pair(N, GT::child_begin(N)));
+ //DOUT << "TarjanSCC: Node " << N <<
+ // " : visitNum = " << visitNum << "\n";
}
// The stack-based DFS traversal; defined below.
void DFSVisitChildren() {
assert(!VisitStack.empty());
- while (VisitStack.back().second != GT::child_end(VisitStack.back().first))
- { // TOS has at least one more child so continue DFS
- NodeType *childN = *VisitStack.back().second++;
- if (nodeVisitNumbers.find(childN) == nodeVisitNumbers.end())
- { // this node has never been seen
- DFSVisitOne(childN);
- }
- else
- {
- unsigned childNum = nodeVisitNumbers[childN];
- if (MinVisitNumStack.back() > childNum)
- MinVisitNumStack.back() = childNum;
- }
+ while (VisitStack.back().second != GT::child_end(VisitStack.back().first)) {
+ // TOS has at least one more child so continue DFS
+ NodeType *childN = *VisitStack.back().second++;
+ if (!nodeVisitNumbers.count(childN)) {
+ // this node has never been seen
+ DFSVisitOne(childN);
+ } else {
+ unsigned childNum = nodeVisitNumbers[childN];
+ if (MinVisitNumStack.back() > childNum)
+ MinVisitNumStack.back() = childNum;
}
+ }
}
// Compute the next SCC using the DFS traversal.
void GetNextSCC() {
assert(VisitStack.size() == MinVisitNumStack.size());
CurrentSCC.clear(); // Prepare to compute the next SCC
- while (! VisitStack.empty())
- {
- DFSVisitChildren();
-
- assert(VisitStack.back().second ==
- GT::child_end(VisitStack.back().first));
- NodeType* visitingN = VisitStack.back().first;
- unsigned minVisitNum = MinVisitNumStack.back();
- VisitStack.pop_back();
- MinVisitNumStack.pop_back();
- if (! MinVisitNumStack.empty() && MinVisitNumStack.back() > minVisitNum)
- MinVisitNumStack.back() = minVisitNum;
-
- //DEBUG(std::cerr << "TarjanSCC: Popped node " << visitingN <<
- // " : minVisitNum = " << minVisitNum << "; Node visit num = " <<
- // nodeVisitNumbers[visitingN] << "\n");
-
- if (minVisitNum == nodeVisitNumbers[visitingN])
- { // A full SCC is on the SCCNodeStack! It includes all nodes below
- // visitingN on the stack. Copy those nodes to CurrentSCC,
- // reset their minVisit values, and return (this suspends
- // the DFS traversal till the next ++).
- do {
- CurrentSCC.push_back(SCCNodeStack.back());
- SCCNodeStack.pop_back();
- nodeVisitNumbers[CurrentSCC.back()] = ~0UL;
- } while (CurrentSCC.back() != visitingN);
- return;
- }
- }
+ while (!VisitStack.empty()) {
+ DFSVisitChildren();
+ assert(VisitStack.back().second ==GT::child_end(VisitStack.back().first));
+ NodeType* visitingN = VisitStack.back().first;
+ unsigned minVisitNum = MinVisitNumStack.back();
+ VisitStack.pop_back();
+ MinVisitNumStack.pop_back();
+ if (!MinVisitNumStack.empty() && MinVisitNumStack.back() > minVisitNum)
+ MinVisitNumStack.back() = minVisitNum;
+
+ //DOUT << "TarjanSCC: Popped node " << visitingN <<
+ // " : minVisitNum = " << minVisitNum << "; Node visit num = " <<
+ // nodeVisitNumbers[visitingN] << "\n";
+
+ if (minVisitNum == nodeVisitNumbers[visitingN]) {
+ // A full SCC is on the SCCNodeStack! It includes all nodes below
+ // visitingN on the stack. Copy those nodes to CurrentSCC,
+ // reset their minVisit values, and return (this suspends
+ // the DFS traversal till the next ++).
+ do {
+ CurrentSCC.push_back(SCCNodeStack.back());
+ SCCNodeStack.pop_back();
+ nodeVisitNumbers[CurrentSCC.back()] = ~0U;
+ } while (CurrentSCC.back() != visitingN);
+ return;
+ }
+ }
}
inline scc_iterator(NodeType *entryN) : visitNum(0) {
return CurrentSCC.empty();
}
- inline bool operator==(const _Self& x) const {
+ inline bool operator==(const _Self& x) const {
return VisitStack == x.VisitStack && CurrentSCC == x.CurrentSCC;
}
inline bool operator!=(const _Self& x) const { return !operator==(x); }
// Iterator traversal: forward iteration only
inline _Self& operator++() { // Preincrement
GetNextSCC();
- return *this;
+ return *this;
}
inline _Self operator++(int) { // Postincrement
- _Self tmp = *this; ++*this; return tmp;
+ _Self tmp = *this; ++*this; return tmp;
}
// Retrieve a reference to the current SCC
- inline const SccTy &operator*() const {
+ inline const SccTy &operator*() const {
assert(!CurrentSCC.empty() && "Dereferencing END SCC iterator!");
return CurrentSCC;
}
- inline SccTy &operator*() {
+ inline SccTy &operator*() {
assert(!CurrentSCC.empty() && "Dereferencing END SCC iterator!");
return CurrentSCC;
}
return scc_iterator<T>::end(G);
}
+} // End llvm namespace
+
#endif
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